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I have a universal spoke wrench. It used to work on any spokes I've owned, until now.

I have a bike with 2mm spokes. The nipples are between a 13 and 14 on the universal spoke wrench's sizes.

I have been able to find a mapping of gauge to mm/in.

I have not been able to find a definitive, trustworthy mapping of gauge/mm/in spoke measurements to gauge/mm/in nipple/spoke wrench measurements.

Can anyone please answer with a definitive, trustworthy mapping like this (except correct):

Spoke Gauge |  in  |  mm  | Nipple Gauge |  in  |  mm
         12 | .036 | 2.3  |            8 | .04  | 3.6
         13 | .076 | 2.4  |            7 | .05  | 3.7
         14 | .016 | 7.6  |            6 | .06  | 3.9
         15 | .026 | 2.3  |            5 | .08  | 5.2
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    Is it possible your nipples are a little worn? Or the spoke tool is slightly oversized now with usage? – Criggie Jan 13 at 10:46
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    nipples are unworn, it's a few months' old bike. possible spoke tool's slightly oversized with usage, but how do i know? – Tom Mercer Jan 13 at 16:46
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    Spoke tools aren't that expensive when compared to ruined nipples. – Carel Jan 13 at 20:20
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    The question can be boiled down to, "How does one buy the correct spoke wrench, every time?". That spoke wrenches are cheap is irrelevant, @Carel – Tom Mercer Jan 13 at 20:48
  • Have you seen bicycles.stackexchange.com/a/63747/19705 ? Its threadded so should close to the right size each time. – Criggie Jan 22 at 19:57
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Nipple wrench flat sizes don't correspond to spoke gauge in as clean or universal of a way as you're suggesting.

This depends a little on where you are in the world (and in histoy), but 2mm aka 14g spokes are by far the most common for bicycles, and there are three different common size nipples associated with them: 0.127", 0.130", and 0.136". (These correspond respectively with the black, green, and red spoke wrenches that several tool companies use.) Of these, the 0.127" wrench flat size is the standard one for 2.0mm spoke nipples by all the modern premium quality spoke makers (DT, Sapim, Wheelsmith, Marwi), and the other two are used seemingly at random by various lower-tier spoke/nipple producers.

Nipples for 1.8mm/15g spokes also almost always have the 0.127" wrench flat size.

2.3mm/13g spoke nipples can have either the 0.136" size or one of the more "oversize" standards like 0.156".

So there is no 1:1 mapping, especially because looking back into history there can be found any number of now-unusual permutations. The gauges listed on ring-type spoke wrenches are arbitrary and outmoded in actual use even if once they were based on some kind of real system.

Also, spoke wrenches in shop use get a lot of reps and do develop slop and eventually wear out.

  • Are you certain about the DT nipples? I cannot get the Park Tool 0.127 in (3.23 mm) key onto my nipples. However, a 3.25 mm key fits. DT Swiss' own spoke key is also specified as a 3.25 mm key. – gschenk Jan 21 at 21:07
  • Taking black Park wrenches to DT nipples has been one of the central activities of my adult life. – Nathan Knutson Jan 21 at 21:08
  • How did you get it on? I have to force the Spokey on. I suppose the black coating is in the way. However, i see no way with the black Park tool, unless, I should use a Hammer or sand either nipples or tool. I also cannot find DT specs for key width. Their tolerances are certainly wider than the 20 μm difference between 0,127" and 3.25 mm. But they ought have chosen a size. – gschenk Jan 21 at 21:20
  • Can you PLEASE format this in a table? You can ignore "now-unusual permutations". You can do x:x mappings since it seems clear that there isn't a 1:1 mapping. – Tom Mercer Jan 22 at 15:08
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There are spoke wreches which compare many different sizes in one tool. Not that expensive either. They look like this:

enter image description here

I have two of these and have thus far not come across a size that wasn't on the tool (working on over 30 bikes.)

  • Read the question. What part of "I have a universal spoke wrench." and "The nipples are between a 13 and 14 on the universal spoke wrench's sizes." do you not understand? – Tom Mercer Jan 22 at 15:06
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    @TomMercer my mistake. – Maarten -Monica for president Jan 22 at 15:07

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